This invention relates to shaded and/or colored dental restorations or prosthesis and methods for their preparation and especially to dental restorations that appear more natural and esthetically appealing.
It has long been known in the dental profession that the good esthetics of dental prostheses are to a significant degree determined by the hue, the chroma and the value of the visibly exposed portions of the dental restoration. These qualities follow the Munsell color system for designating color which employs three perceptually uniform scales (Munsell hue, Munsell value and Munsell chroma) defined in terms of daylight reflection. (McGraw-Hill Dictionary of Scientific and Technical Terms--3rd Ed.). Translucency or the quality of transmitting and diffusing light, which gives a perception of depth is also an important parameter.
Insofar as is known, in the past it has been considered necessary in producing esthetically satisfactory artificial tooth restorations that are of the nature of facings, by which it is meant to include crowns and veneers, to build the facing's color throughout all of the light passing or translucent portions thereof. By throughout all the translucent portions it is meant the entire depth of the tooth prosthesis through which light passes to the eye of an observer. Building the color throughout the depth of the dental restoration is certainly logical from the standpoint that a natural tooth does build the color throughout its depth.
It has now been discovered, however, that what might be called an optical illusion of a natural tooth appearance can be achieved by not coloring the dental prosthesis facing throughout its entire light passing depth but instead by applying an opaquing layer of specific hue and chroma overlayed with a translucent build up layer that is substantially hue and chroma free while being translucent to light and applying a shader over this uncolored layer to provide a final esthetic effect. Not only is the appearance superior but the number of build up material variations that are required to match the unique variation in natural teeth can be reduced from about 40 to a single build up material being required to satisfy substantially all of the application requirements. No shading is required between the underlying opaquing layer and the outer shader layer.
In at least one instance on a commercial basis during the 1950's and continuing at least into the 1960's, an artificial anterior tooth 33 was constructed that is represented in FIG. 4 and had an opaque lingual area 31 that did not extend to the proximity of the incisal edge of the tooth but extended interiorly past the center portion of the tooth. The opaque area was composed of a very heavily pigmented porcelain with very strong hue and chroma to the extent of substantially complete opacity. Frontwardly of this opaque area was a layer 35 of shaded porcelain having very substantial hue and chroma but retaining substantial translucency. Forwardly of layer 35 and also upwardly toward the incisal edge of the tooth is a translucent layer 36 that is substantially hue and chroma free porcelain and also substantially clear, like water. This layer 36 opens to the incisal edge of the tooth and also overlays the shaded layer 35 at the incisal lingual portion of the tooth. The labial face of the tooth has a layer 37 of pigmented porcelain having substantially no hue, being pigmented to a substantially enamal white. To this layer 37 was added as a surface coat (not shown) various shading colors mixed with a porcelain overglaze to characterize the individual teeth to more natural appearances.
To make the tooth 33, the sequence is to make the opaque portion 31 and the portion of the layer 36 above portion 31 and rearwardly of layer 35. Also independently the layer 37 and 36, except for the portion already described in the preceeding sentence is made. Then the parts are joined through layer 35.
It is known that some of the teeth 33 of FIG. 4 were ground off from the back as shown at line 5--5 of FIG. 4 to form the veneer 40 of FIG. 5, which veneer was then adhered to a metal prosthetic support part 41 shown broken away at its base. The veneer thus had an opaque metal substrate 41, an opaque cement layer 42 applied to the front face or labial face of the metal support to become a part of the support, a shaded porcelain layer 43 having substantial hue and chroma, a substantially hue and chroma free porcelain layer 44 and a labial surface layer 45 of pigmented porcelain having substantially no hue to which was added a surface shading material (not shown) as described above.
It is an object of the present invention to provide dental restorations with superior esthetic appearance.
It is a further object of the present invention to provide an easier method of producing superior esthetic dental restorations.
It is a still further object of the present invention to provide a method of producing dental restorations that enable less expensive correction of mistakenly produced hues, chromas and values.